package com.hmdp.service.impl;

import cn.hutool.core.bean.BeanUtil;
import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisConstants;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;

    @Override
    public Result queryById(Long id) {
        // 缓存穿透
        // Shop = shop = queryWithPassThough(id);
        //
        Shop shop = cacheClient.queryWithPassThrough(
                CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);

        //互斥锁解决缓存穿透
//        Shop shop = queryWithMutex(id);

        // 逻辑过期
//        Shop shop = queryWithLogicExpire(id);

        if(shop == null){
            return Result.fail("店铺不存在！");
        }
        return Result.ok(shop);

    }
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public Shop queryWithLogicExpire(Long id) {
        String key = CACHE_SHOP_KEY + id;

        // 1.从redis差缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        // 2.判断是否存在
        if(StrUtil.isBlank(shopJson)){
            // 3.不存在，返回
            return null;
        }

        // 4.命中，判断过期时间，Json反序列化对象，
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject)redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();

        // 5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            // 未过期，返回信息
            return shop;
        }
        // 过期，需要缓存重建
        // 6.缓存重建
        String lockKey = LOCK_SHOP_KEY + id;
        boolean islock = tryLock(lockKey);

        // 判断获取互斥锁
        if(islock){
            // 成功，开启线程实现重建
            // TODO
            expireTime = redisData.getExpireTime();
            // 5.判断是否过期
            if(expireTime.isAfter(LocalDateTime.now())){
                // 未过期，返回信息
                return shop;
            }
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                // 重建
                try {
                    this.save2ShopToRedis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    // 释放锁
                    unlock(lockKey);
                }
            });

        }

        // 返回商铺信息
        return shop;
    }

    public Shop queryWithMutex(Long id) {
        String key = CACHE_SHOP_KEY + id;

        // 1.从redis差缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        // 2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)){
            // 3.存在，返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class, true);
            return shop;
        }
        // 查询命中的是否是空值
        if(shopJson == null){
            return null;
        }

        // 开始实现缓存重建
        // 获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;

        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            // 判断是否成功
            if(!isLock){
                Thread.sleep(50);
                queryWithMutex(id);
            }
            // 失败休眠并重拾

            // 4.成功， 先查数据库根据id
            shop = getById(id);
            // 模拟重建
            Thread.sleep(200);
            // 5.不存在，返回错误
            if(shop == null){
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }
            // 6.存在，写入redis 返回
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            // 释放互斥锁
            unlock(lockKey);
        }
        return shop;
    }

//    public Shop queryWithPassThrough(Long id) {
//        String key = CACHE_SHOP_KEY + id;
//
//        // 1.从redis差缓存
//        String shopJson = stringRedisTemplate.opsForValue().get(key);
//
//        // 2.判断是否存在
//        if(StrUtil.isNotBlank(shopJson)){
//            // 3.存在，返回
//            Shop shop = JSONUtil.toBean(shopJson, Shop.class, true);
//            return shop;
//        }
//        // 查询命中的是否是空值
//        if(shopJson == null){
//            return null;
//        }
//
//        // 4.不存在， 先查数据库根据id
//        Shop shop = getById(id);
//        // 5.不存在，返回错误
//        if(shop != null){
//            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
//            return null;
//        }
//        // 6.存在，写入redis 返回
//        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
//
//        return shop;
//    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }

    public void save2ShopToRedis(Long id, Long expireSeconds) throws InterruptedException {
        // 1.查询店铺数据
        Shop shop = getById(id);
        Thread.sleep(200);
        // 2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        // 3.写入Redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        if(shop.getId() == null){
            return Result.fail("店铺id不能为0");
        }
        // 1.更新数据库后更新缓存
        updateById(shop);
        // 2.删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + shop.getId());
        return Result.ok();
    }
}
